                          "The Blue Box And Ma Bell"
                     Herb Friedman, Communications Editor
                           Radio Electroncs Magazine
                                 November 1987

                                  Typed By :
                                Cardiac Arrest
                                    06/89

     Before the breakup of AT&T, Ma Bell was everyone's favorite
enemy.  So it was not surprising that so many people worked so
hard and so successfully at perfecting various means of making
free and untracable telephone calls.  Whether it was a "Red Box"
used by Joe and Jane College to call home, or a "Blue Box" used
by organized crime to lay off untracable bets, the technology
that provided the finest telephone system in the world contained
the seeds of it's own destruction.

        The fact of the matter is that the Blue Box was so
effective at making untracable calls that there is no estimate
as to how many calls were made or who made them.  No one knows
for certain whether Ma Bell lost revenues of $100, $100-million,
or $1-billion on the Blue Box.  Blue Boxes were so effective at
making free, untracable calls that Ma Bell didn't want anyone to
know about them, and for many years denied their existence.
They even went as far as strong-arming a major consumer science
magazine into killing an article that had already been prepared
on the Blue and Red boxes.  Further, the police records of a
major city contain a report concerning a break-in at the
residence of the author of that article.  The only item missing
following the break-in was the folder containing copies of the
earliest Blue-Box designs and a Bell-System booklet that
described how subscriber billing was done by the AMA machine--a
booklet that Ma Bell denied ever existed [article includes
picture proving otherwise - Cardiac].  Since the AMA (Automatic
Message Accounting) machine was the means whereby Ma Bell
eventually tracked down both the Blue and Red Boxes, we'll take
time out to explain it.  Besides, knowing how the AMA machine
works will help you to better understand "phone phreaking."

WHO MADE THE CALL

        Back in the early days of the telephone, a customer's
billing was originated in a mechanical counting device, which
was usually called a "register" or a "meter."  Each subscriber's
line was connected to a meter that was part of a wall of meters.
The meter clicked off the message units, and once a month
someone simply wrote down the meter's reading, which was later
interpolated into message-unit billing for those subscriber's
who were charged by the message unit.  (Flat rate subscriber's
could make unlimited calls only within a designated geographic
area.  The meter clicked off message units for calls outside
that area.)  Because eventually there were too many meters to
read individually, and because more subscribers started
questioning their monthly bills, the local telephone companies
turned to photography.  A photograph of a large number of meters
served as an incontestable record of their reading at a given
date and time, and was much easier to convert to customer
billing by the accounting department.

        As you might imagine, even with photographs billing was
cumbersome and did not reflect the latest technical
developments.  A meter didn't provide any indication of what the
subscriber was doing with the telephone, nor did it indicate how
the average subscriber made calls or the efficiency of the
information service (how fast the operators could handle
requests).  So the meters were replaced by the AMA machine.  One
machine handled up to 20,000 subscribers.  It produced a punched
tape for a 24-hour period that showed, among other things, the
time a phone was picked up (went off-hook), the number dialed,
the time the called party answered, and the time the originating
phone was hung up (placed on-hook).

        One other point, which will answer some questions that
you're certain to think of as we discuss the Red and Blue boxes:
Ma Bell did not want persons outside their system to know about
the AMA machine.  The reason?  Almost everyone had
complaints--usually unjustified--about their billing.  Had the
public been aware of the AMA machine they would have asked for a
monthly list of their telephone calls.  It wasn't that Ma Bell
feared errors in billing; rather, they were fearful of being
buried under an avalanche of paperwork and customer complaints.
Also, the public beleived their telephone calls were personal
and untraceable, and Ma Bell didn't want to admit that they knew
about the who, when, and where of every call.  And so Ma
Bellalways insisted that billing was based on a meter unit that
simply "clicked" for each message unit; thatthere was no record,
other than for long-distance calls, as to who called whom.  Long
distance was handled by, and the billing information was done by
and operator, so there was a written record Ma Bell could not
deny.

        The secrecy surrounding the AMA machine was so pervasive
that local, state, and even federal police were told that local
calls made by criminals were untraceable, and that people who
made obscene telephone calls could not be tracked down unless
the person receiving the cals could keep the caller on the line
for some 30 to 50 minutes so the connections could be physically
traced by technicians.  Imagine asking a woman or child to put
up with almost an hours worth of the most horrendous obscenities
in the hope someone could trace the line.  Yet in areas where
the AMA machine had replaced meters, it would have been a
simple, though perhaps time-consuming task, to track down the
numbers called by any telephone during a 24-hour period.  But Ma
Bell wanted the AMA machince kept as secret as possible, and so
many a criminal was not caught, and many a woman was harried by
the obscene calls of a potential rapist, because existence of
the AMA machine was denied.

        As a sidelight as to the secrecy surrounding the AMA
machine, someone at Ma Bell or the local operating company
decided to put the squeeze on the author of the article on Blue
Boxes, and reported to the treasury Department that he was, in
fact, manufacturing them for organized crime--the going rate in
the mid 1960's was supposedly $20,000 a box.  (Perhaps Ma Bell
figured the author would get the obvious message: Forget about
the Blue Box and the AMA machine or you'll spend lots of time,
and much money on lawyer's fees to get out of the hassles it
will cause.)  The author was suddenly visited ay his place of
employment by a Treasury agent.  Fortunately, it took just a few
minutes to convince the agent that the author was really just
that, and the a technical wizard working for the mob.  But one
conversation led to another, and the Treasury agent was
astounded to learn about the AMA machine.  (Wow!  Can an author
whose story is squelched spill his guts.)  According to the
treasury agent, his department had been told that it was
impossible to get a record of local calls made by gangsters: The
Treasury department had never been informed of the existence of
automatic message accounting.  Needless to say, the agent left
with his own copy of the Bell System publication about the AMA
machine, and the author had an appointment with the local
Treasury-Bureau director to fill him in on the AMA Machine.
That information eventually ended up with Senator Dodd, who was
conducting a congressional investigation into, among other
things, telephone company surveillance of subscriber
lines--which was a common practice for which there was detailed
instructions, Ma Bell's own switching equipment ("crossbar")
manual.

THE BLUE BOX

        The Blue Box permitted free telephone calls because it
used Ma Bell's own internal frequency-sensitive circuits.  When
direct long-distance dialing was introduced, the crossbar
equipment knew a long-distance call was being dialed by the
three-digit area code.  The crossbar then converted the dial
pulses the the CCITT tone groups, shown in Table 1 [I'll put the
table in at the end of the file - Cardiac], that are used for
international and truckline signalling.  (Not that those do not
correspond to Touch-Tone frequencies.)  As you can see in that
table, the tone groups represent more than just numbers; among
other things there are tone groups indentified as KP (prime) and
ST (start)--keep them in mind.  When a subscriber dialed an area
code and a telephone number on a rotary-dial telephone, the
crossbar automatically conneceted the subscriber's telephone to
a long-distance truck, converted the dial pulses to CCITT tones
sent out on the long-distance trunk that set up or selected the
routing and caused electro-mechanical equipment in the target
city to dial the called telephone.

        Operator-assisted long-distance calls worked the same
way.  The operator simply logged into a long-distance trunk and
pushed the appropriate buttons, which generated the same tones
as direct-dial equipment.  The button sequence was KP (which
activated the long-distance equipment), then the complete area
code and telephone number.  At the target city, the connection
was made to the called number but ringing did not occur until
the operator there pressed the ST button.  The sequence of
events of early Blue Boxes went like this: The caller dialed
information in a distant city, which caused his AMA machine to
record a free call to information.  When the information
operator answered, he pressed the KP key on the Blue Box, which
disconnected the operator and gave him access to a long-distance
trunk.  He then dialed the desired number and ended with an ST,
which caused the target phone to ring.  For as long as the
conversation took place, the AMA machine indicated a free call
to an information operator.  The technique required a
long-distance information operator because the local operator,
not being on a long-distance trunk, was accessed through local
wire switching, not the CCITT tones.

CALL ANYWHERE

        Now imagine the possibilities.  Assume the Blue Box user
was in Philadelphia.  He would call Chicago information,
disconnect from the operator with a KP tone, and then dial
anywhere that was on direct-dialing service: Los Angeles,
Dallas, or anywhere in the world in the Blue Boxer could get the
internatioal codes.

        The legend often told of one Blue Boxer who, in the
1960's, lived in New York and had a girlfriend at a college near
Boston.  Now back in the 1960's, making a telephone call to a
college town on the weekend was even more difficult than it is
today to make a call from New York to Florida on a reduced-rate
holiday using one of the cut-rate long-distance carriers.  So
our Blue Boxer got on an international operator's circuit to
Rome, Blue Boxed through to a Hamburg operator, and asked
Hamburg to patch through to Boston.  The Hamburg operator
thought the call originated in Rome and inquired as to the
"operator's" good English, to which the Blue Boxer replied that
he was an expatriate hired to handle calls by American tourists
back to their homeland.  Every weekend, while the Northeast was
strangled by reduced-rate long-distance calls, our Blue Boxer
had no trouble sending his voice almost 7,000 miles for free.

VACUUM TUBES

        Assembly plans for Blue Boxes were sold through
classified advertisements in the electronic-hobbyist magazines.
One of the earliest designs was a two-tube poertable model that
used a 1.5-volt "A" battery for the filaments and a 125-volt "B"
battery for the high-voltage (B+) power supply.  The portable
Blue Box's functional circuit in shown in Fig. 2 [It's nothing
you can't find in any good Blue Box g-file, so I won't try to
draw it - Cardiac].  it consisted of two phase-shift oscillators
sharing a common speaker that mixed the tones from both
oscillators.  Switches S1 and S2 each represent 12 switching
circuits used to generate the tones. (No, we will not supply a
working circuit, so please don't write in and
ask--Editor)[That's the real editor, not me - Cardiac]  The user
placed the speaker over the telephone handset's transmitter and
simply pressed the buttons that corresponded to the disired
CCITT tones.  It was just that simple.

        Actually, it was even easier then it reads because Blue
Boxers dicovered they did not need the operator.  If they dialed
an active telephone located in certain nearby, but different,
area codes, they could Blue Box just as if they had Blue Boxed
through an information operator's circuit.  The subscriber whose
line was blue Box conversatio was short, the "dead" phone
suddenly came to life the next time it was picked up.  Using a
list of "distant" numbers, a Blue Boxer would never hassle plain
to the telephone company.  The difference between Blue Boxing
off a subscriber rather than an informatio operator was that the
Blue Boxer's AMA tape indicated a real long-distance telephone
call--perhaps costing 15 or 25 cents--instead of a freebie.  Of
course, that is the reason why when Ma Bell finally decided to
go public with "assisted" newspaper articles about the Blue Box
users they had apprehended, it was usually about some college
kid or "phone phreak."  One never read of a mobster being
caught.  Greed and stupidity were the reasons why the kid's were
caught.  It was the transistor that led to Ma Bell going public
with the Blue Box.  By using transistors and RC phase-shift
networks for the oscillators, a portable Blue Box could be made
inexpensively, and small enough to be used unobstrusively from a
public telephone.  The college crowdin the many technical
schools went crazy with the partable Blue Box; they could call
the folks back home, their friends, or get a free network (the
Alberta and Carolina connections--which could be a topic for a
whole separate article) and never pay a dime to Ma Bell.  Unlike
the mobsters who were willing to pay a small long-distance
charge when Blue Boxing, the kids wanted it, wanted it all free,
and so they used the information operator routing, and would
often talk "free-of-charge" for hours on end.

        Ma Bell finally realized that Blue Boxing was costing
them big bucks, and decided a few articles on the criminal
penalties might scare the Blue Boxers enough to cease and
desist.  But who did Ma Bell catch?  The college kids and the
greedies.  When Ma Bell decided to catch the Blue Boxers she
simply examined the AMA tapes for calls to an information
operator that were excessively long.  No one talked to an
operator for 5, 10, 30 minutes, or several hours.  Once a long
call to an operator appeared several times on an AMA tape, Ma
Bell simply monitored the line and the Blue Boxer was caught.
(Now do you understand why we opened with an explanation of the
AMA machince?) If the Blue Boxer worked from a telephone boothk,
Ma Bell simply monitored the booth.  Ma Bell might not have
known who originated the call, but she did know who got the
call, and getting that party to spill their guts was no problem.
The mob and a few Blue Box hobbyists (maybe even thousands) knew
of the AMA machine, and so they used a real telephone number for
the KP skip.  Their AMA tapes looked perfectly legitimate.  Even
if Ma Bell had told the authorities they could provide a list of
direct-dialed calls made by local mobsters, the AMA tapes would
never show who was called through a Blue Box.  For example, if a
bookmaker in New York wanted to lay off some action in Chicago,
he could make a legitimate call to a phone in New Jersey and
then Blue Box to Chicago.  Of course, automatic tone monitoring,
computerized billing, and ESS (Electronic Switchin Systems) now
make that all virtually impossible. but that's the way it was.

        You might wonder how Ma Bell discovered the tricks of
the Blue Boxers.  Simple, they hired the perpetrators as
consultants.  While the initial newspaper articles detailed the
potential jail penalties for apprehended Blue Boxers, except for
Ma Bell employees who assisted a Blue Boxer, it is almost
impossible to find an article on the resolution of the cases
because most hobbyist Blue Boxers got suspended sentences and/or
probation if they assisted Ma Bell in developing anti-Blue Box
techniques.  It is asserted, although it can't be easily proven,
that cooperating ex-Blue Boxers were paid as consultants.  (If
you can't beat them, hire them to work for you.)

        Should you get any ideas about Blue Boxing, keep in mind
that modern switching equipment has the capacity to recognize
unauthorized tones.  It's the reason why a local office can
leave their subscriber Touch-Tone circuits actives, almost
inviting you to use the Touch-Tone service.  A few days after
you use an unauthorized Touch-Tone service, the business office
will call and inquire whether you'd like to pay for the service
or have it disconnected.  The very same central-office equipment
that knows you're using Touch-Tone frequencies knows if your
line is originating CCITT signals.

THE RED BOX

        The Red Box was primarily used by the college crowd to
avoid charges when fequent calls were made between two
particular locations, say the college and a student's home.
Unlike the somewhat complex circuitry of the Blue Box, a Red Box
was nothing more than a modified telephone; in some instances
nothing more than a capacitor, a momentary switch, and a
battery.  As you recall from our discussion of the Blue Box, a
telephone circuit is really established before the target phone
ever rings, and the circuit is capable of carrying an AC signal
in either direction.  When the caller hears the ringing in his
or her handset, nothing is happening at the receiving end
because the ringing signal he hears is really a tone generator
at his local telephone office.  The target (called) telephone
actually gets it 20 pulses-per-second ringing voltage when the
person who dialed hears nothing--in the "dead" spaces between
hearing the ringing tone.  When the called phone is answered and
taken off hook, the telephone completes a local-office DC loop
that is the signal to stop the ringing voltage.  About three
seconds later the DC loop results in a signal being sent all the
way back to the caller's AMA machine that the called telephone
was answered.  Keep that three-second AMA delay in mind.  (By
now you should have a pretty good idea of what's coming!) [I'm
skipping a paragraph talking about how a telephone circuit
works.  It is referring to a simple phone schematic that isn't
worth drawing, so I ommited the whole paragraph - Cardiac] Now
as we said earlier, the circuit can actually carry AC before the
DC loop is closed.  The Red Box is simply a device that provides
a telephone with a local battery so that the phone can generate
an AC signal without having a DC connection to the telephone
line.  The earliest of the Red Boxes was the surplus military
field telephone, of which there were thousands upon thousands in
the marketplace during the 1950's and 1960's.  The field
telephone was a portable telephone unit having a manual ringer
worked by a crank--just like the telephone Grandpa used on the
farm--and two D-cells.  A selector switch set up the unit so
that it could be connected to a combat switchboard, with the DC
power supplied by the switchboard.  But if a combat unit wasn't
connected to a switchboard, and the Lieutenant yelled "Take a
wire," the signalman threw a switch on his field telephone that
switched in the local batteries.  To prevent the possibility of
having both ends of the circuit feeding battery current into the
line in opposite polarity--thereby resulting in silence--the
output from the field telephone when running from its internal
batteries was only the AC representing the voice input, not
modulated DC.  [I ommited the next two paragraphs, which talk
about how to make one.  It too has a complicated schematic, so I
wont draw it.  It's the same stuff you get from any Red Box
g-file - Cardiac]

PRESS ONCE TO TALK

        The Red Box was used at the receiving end; let's assume
it's the old homestead.  The call was originated by Junior (or
Sis) at their college 1000 miles away from home.  Joe gave the
family one ring and then hung up, which told them that he's
calling.  Pop set up the Red Box.  Then Junior redialed the old
homestead.  Pop lifted the handset when the phone rang.  Then
Pop closed a momentary-switch for about a half-second, which
caused the local telephone office to silence the ringing signal.
When Pop released the switch, the folks cantalk to Junior
without Junior getting charged because his AMA tape did not show
his call was answered--the DC loop must be closed for at least
three-seconds for the AMA tape to show Junior's call was
answered.  All the AMA tape showed is that Junior let the phone
ring at the old homestead for almost 30 minutes; a length of
time that no Bell Operating Company is likely to believe twice!

        A modern Red Box is simpy a conventional telephone
that's been modified to emulate the vintage 1940 military field
telephone.  Aside from the fact that the operating companies can
now nail every Red Box user because all modern billing equipment
shows the AMA information concerning the length of time a caller
let the target phone ring, it's use has often put severe
psychological strain on the users.

        [I ommited another paragraph here.  It was just some
closing stuff.  Nothing special - Cardiac]

        There are no hard facts concerning how many Red Boxes
were in use, or how much money Ma Bell lost, but one thing is
known: she had little difficulty in closing down Red Boxes in
virtually all instances where the old folks were involved
because Mom and Pop usually would not tolerate what to them was
stealing.  If you as a reader have any ideas about using a Red
Box, bear in mind that the AMA machine (or it's equivilent) will
get you every time, even if you use a phone booth, because the
record will show the number being called, and as with the Blue
Box, the people on the receiving end will spill their guts to
the cops.
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